File locked - can't be deleted; Nextcloud is quiet slow (approx 9MB/s, even for big files)

first the wanted informations:

Nextcloud version: 11.0.2
Operating system and version: Ubuntu Server 16.10
Apache or nginx version: Apache 2.4.18
PHP version 7.0.15
Is this the first time you’ve seen this error?: Yes
Encryption is enabled

Can you reliably replicate it? (If so, please outline steps): Trying to delete this one file.

The issue you are facing:
If I try to delete one .mp4 file from the “basefolder” of nextcloud I get the message “Error deleting file xxx.mp4”

The output of your Nextcloud log in Admin > Logging:
Fatal webdav OCA\DAV\Connector\Sabre\Exception\FileLocked: HTTP/1.1 423 “xxx.mp4” is locked
/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Tree.php - line 179: OCA\DAV\Connector\Sabre\File->delete()
/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/CorePlugin.php - line 287: Sabre\DAV\Tree->delete(‘2017_02_05_18_5…’)
[internal function] Sabre\DAV\CorePlugin->httpDelete(Object(Sabre\HTTP\Request), Object(Sabre\HTTP\Response))
/var/www/nextcloud/3rdparty/sabre/event/lib/EventEmitterTrait.php - line 105: call_user_func_array(Array, Array)
/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php - line 479: Sabre\Event\EventEmitter->emit(‘method DELETE’, Array)
/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php - line 254: Sabre\DAV\Server->invokeMethod(Object(Sabre\HTTP\Request), Object(Sabre\HTTP\Response))
/var/www/nextcloud/apps/dav/appinfo/v1/webdav.php - line 60: Sabre\DAV\Server->exec()
/var/www/nextcloud/remote.php - line 165: require_once(’/var/www/nextcl…’)


Error PHP Uncaught Error: Access to undeclared static property: OC\Files\Filesystem::$normalizedPathCache in /var/www/nextcloud/lib/private/Files/Filesystem.php:806 Stack trace: #0 /var/www/nextcloud/lib/private/Files/View.php(2018): OC\Files\Filesystem::normalizePath(’/niemand/files/…’) #1 /var/www/nextcloud/lib/private/Files/View.php(1156): OC\Files\View->unlockFile(’/xxx.mp4…’, 1) #2 [internal function]: OC\Files\View->OC\Files{closure}() #3 /var/www/nextcloud/3rdparty/icewind/streams/src/CallbackWrapper.php(109): call_user_func(Object(Closure)) #4 [internal function]: Icewind\Streams\CallbackWrapper->stream_close() #5 {main} thrown at /var/www/nextcloud/lib/private/Files/Filesystem.php#806

The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):

<?php $CONFIG = array ( 'instanceid' => 'XXX', 'passwordsalt' => 'XXX', 'secret' => 'XXX', 'trusted_domains' => array ( 0 => '', 1 => 'XXX', ), 'datadirectory' => '/mnt/disk2/nextcloud', 'overwrite.cli.url' => '', 'dbtype' => 'mysql', 'version' => '', 'dbname' => 'XXX', 'dbhost' => 'localhost', 'dbport' => '', 'dbtableprefix' => 'oc_', 'dbuser' => 'XXX', 'dbpassword' => 'XXX', 'logtimezone' => 'UTC', 'installed' => true, 'memcache.local' => '\\OC\\Memcache\\APCu', 'loglevel' => 2, 'maintenance' => false, 'theme' => '', 'mail_smtpmode' => 'smtp', 'mail_smtpsecure' => 'tls', 'mail_from_address' => 'XXX', 'mail_domain' => 'XXX', 'mail_smtpauthtype' => 'LOGIN', 'mail_smtpauth' => 1, 'mail_smtphost' => 'XXX', 'mail_smtpport' => '587', 'mail_smtpname' => 'XXX', 'mail_smtppassword' => 'XXX', 'updater.secret' => 'XXX', ); The output of your Apache/nginx/system log in `/var/log/____`: what you need? They're not having some great error in them. and the second problem is that it is quiet slow over LAN (1Gbit) with only 9MB/s transferspeed. any improvements? Without this problems Nextcloud ran for month very smoothly and I don't want to miss it anymore! So please help :) Thanks alot.

I found this one here: Dateien lassen sich nicht löschen and the post from Ventusfahrer helped!
I could delete it, yeah!

BUT a new problem occurs.
The Nextcloud is running in an Proxmox-VM. I gave a 160GB Container to the Nextcloud-VM and I gave 90GB to my standard-user. Only 84GB have been shown as available, that would have been still ok, but after deleting of this locked file I only got 76.4 GB of available space left?? where’s the rest gone? I can resize it to a lower value, but not to a higher one. What can I do? And how could I expand the maximum available space to the 160GB?